Theoretical investigation of hydrogen storage ability of a carbon nanohorn

The carbon nanohorn due to severe curvature could bind hydrogen molecule through enhanced binding at the top section adjacent to its closed top end. The storage capacity limited by the room at the top end section is only 1.8 wt.% for hydrogen to be captured inside the studied nanohorn. Li atoms are found to adhere on the sidewalls of nanohorn separately at low Li atom content rather than aggregate. Each Li atom on the outer sidewall could bind three hydrogen molecules, while the small room inside the nanohorn limits the adsorbed hydrogen molecules to be eight at maximum. The hydrogen binding energy attracted by Li atoms would not be altered much if both sidewalls are decorated by Li atoms. The total storage capacity could be 5.8 wt.% with 8 and 36 H2 respectively adsorbed surrounding the Li atoms on the inner and the outer sidewalls, which has the average binding energy per H2 > 200 meV. By adsorbing 24 more H2 with binding energy of ∼160 meV/H2 on the outer sidewall at the large hollow space circled by neighboring Li atoms and their attracted hydrogen molecules, the capacity of 8.6 wt.% could be obtained.